Projection optical system and exposure apparatus using the same

ABSTRACT

The present invention relates to an exposure apparatus using a projection optical system to realize a small size and the bitelecentricity as securing a wide exposure area and a large numerical aperture and to realize extremely good correction for aberrations, particularly for distortion. The projection optical system comprises a first lens group G 1  with a positive refracting power, a second lens group G 2  with a negative refracting power, a third lens group G 3  with a positive refracting power, a fourth lens group G 4  with a negative refracting power, a fifth lens group G 5  with a positive refracting power, and a sixth lens group G 6  with a positive refracting power in order from the side of the first object R, wherein the second lens group G 2  comprises a front lens L 2F  with a negative refracting power, a rear lens L 2R  of a negative meniscus shape, and an intermediate lens group G 2M  disposed between the front lens and the rear lens, and wherein the intermediate lens group G 2M  has a first lens L M1  with a positive refracting power, a second lens L M2  with a negative refracting power, and a third lens L M3  with a negative refracting power in order from the side of the first object R. The system is arranged to satisfy within suitable ranges of focal lengths for the first to sixth lens groups G 1  -G 6 , based on the above arrangement.

This is a continuation of application Ser. No. 08/516,903, filed Aug.18, 1995, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure apparatus having aprojection optical system for projecting a pattern of a first objectonto a photosensitive substrate etc. as a second object, and moreparticularly to a projection optical system suitably applicable toprojection exposure of a pattern for semiconductor or liquid crystalformed on a reticle (mask) as the first object onto the substrate(semiconductor wafer, plate, etc.) as the second object.

2. Related Background Art

As the patterns of integrated circuits become finer and finer, theresolving power required for the exposure apparatus used in printing ofwafer also becomes higher and higher. In addition to the improvement inresolving power, the projection optical systems of the exposureapparatus are required to decrease image stress. In order to get readyfor the finer tendency of transfer patterns, light sources for exposurehave recently been changing from those emitting the light of exposurewavelength of the g-line (436 nm) to those emitting the light ofexposure wavelength of the i-line (365 nm) that are mainly used atpresent. Further, a trend is to use light sources emitting shorterwavelengths, for example the excimer laser (KrF:248 nm, ArF:193 nm).

Here, the image stress includes those due to bowing etc. of the printedwafer on the image side of projection optical system and those due tobowing etc. of the reticle with circuit pattern etc. written therein, onthe object side of projection optical system, as well as distortioncaused by the projection optical system.

With a recent further progress of fineness tendency of transferpatterns, demands to decrease the image stress are also becoming harder.

Then, in order to decrease effects of the wafer bowing on the imagestress, the conventional technology has employed the so-calledimage-side telecentric optical system that located the exit pupilposition at a farther point on the image side of projection opticalsystem.

On the other hand, the image stress due to the bowing of reticle canalso be reduced by employing a so-called object-side telecentric opticalsystem that locates the entrance pupil position of projection opticalsystem at a farther point from the object plane, and there aresuggestions to locate the entrance pupil position of projection opticalsystem at a relatively far position from the object plane as described.Examples of those suggestions are described for example in JapaneseLaid-open Patent Applications No. 63-118115 and No. 5-173065 and U.S.Pat. No. 5,260,832.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a high-performanceprojection optical system which can achieve the bitelecentricity in acompact design as securing a wide exposure area and a large numericalaperture and which can be well corrected for aberrations, particularlywhich can be very well corrected for distortion. The projection opticalsystem can be applied to an exposure apparatus.

To achieve the above object, an exposure apparatus according to thepresent invention comprises at least a wafer stage allowing aphotosensitive substrate to be held on a main surface thereof, anillumination optical system for emitting exposure light of apredetermined wavelength and transferring a predetermined pattern of amask (reticle) onto the substrate, a projection optical system providedbetween a first surface on which the mask as a first object is disposedand a second surface on which a surface of the substrate as a secondobject is corresponded, for projecting an image of the pattern of themask onto the substrate. The illumination optical system includes analignment optical system for adjusting a relative positions between themask and the wafer, and the mask is disposed on a reticle stage which ismovable in parallel with respect to the main surface of the wafer stage.The projection optical system has a space permitting an aperture stop tobe set therein. The photosensitive substrate comprises a wafer such as asilicon wafer or a glass plate, etc., and a photosensitive material suchas a photoresist or the like coating a surface of the wafer. Inparticular, as shown in FIG. 1, the projection optical system includes afirst lens group (G₁) with a positive refracting power, a second lensgroup (G₂) with a negative refracting power, a third lens group (G₃)with a positive refracting power, a fourth lens group (G₄) with anegative refracting power, a fifth lens group (G₅) with a positiverefracting power, and a sixth lens group (G₆) with a positive refractingpower in order from the side of the first object (for example, a mask).

The second lens group (G₂) comprises a front lens (L_(2F)) with anegative refracting power disposed as closest to the first object andshaded with a concave surface to the second object, a rear lens (L_(2R))of a negative meniscus shape disposed as closest to the substrate andshaped with a concave surface to the mask, and an intermediate lensgroup (G_(2M)) disposed between the front lens (L_(2F)) and the rearlens (L_(2R)). In particular, the intermediate lens group (G_(2M)) has afirst lens (L_(M1)) with a positive refracting power, a second lens(L_(M2)) with a negative refracting power, and a third lens (L_(M3))with a negative refracting power in order from the side of the firstobject.

Further, the projection optical system according to the presentinvention is arranged to satisfy the following conditions (1) to (6)when f₁ is a focal length of the first lens group (G₁), f₂ is a focallength of the second lens group (G₂), f₃ is a focal length of the thirdlens group (G₃), f₄ is a focal length of the fourth lens group (G₄), f₅is a focal length of the fifth lens group (G₅), f₆ is a focal length ofthe sixth lens group (G₆), and L is a distance from the first object tothe second object:

(1) f₁ /L<0.8

(2) -0.033<f₂ /L

(3) 0.01<f₃ /L<1.0

(4) f₄ /L<-0.005

(5) 0.01<f₅ /L<0.9

(6) 0.02<f₆ /L<1.6.

The projection optical system is so arranged as to have at least thefirst lens group (G₁) with positive refracting power, the second lensgroup (G₂) with negative refracting power, the third lens group (G₃)with positive refracting power, the fourth lens group (G₄) with negativerefracting power, the fifth lens group (G₅) with positive refractingpower, and the sixth lens group (G₆) with positive refracting power inthe named order from the first object side.

First, the first lens group (G₁) with positive refracting powercontributes mainly to a correction of distortion while maintainingtelecentricity, and specifically, the first lens group (G₁) is arrangedto generate a positive distortion to correct in a good balance negativedistortions caused by the plurality of lens groups located on the secondobject side after the first lens group (G₁). The second lens group (G₂)with negative refracting power and the fourth lens group (G₄) withnegative refracting power contribute mainly to a correction of Petzvalsum to make the image plane flat. The two lens groups of the second lensgroup (G₂) with negative refracting power and the third lens group (G₃)with positive refracting power form an inverse telescopic system tocontribute to guarantee of back focus (a distance from an opticalsurface such as a lens surface closest to the second object in theprojection optical system to the second object) in the projectionoptical system. The fifth lens group (G₅) with positive refracting powerand the sixth lens group (G₆) similarly with positive refracting powercontribute mainly to suppressing generation of distortion andsuppressing generation particularly of spherical aberration as much aspossible in order to fully support high NA structure on the secondobject side.

Based on the above arrangement, the front lens (L_(2F)) with thenegative refracting power disposed as closest to the first object in thesecond lens group (G₂) and shaped with the concave surface to the secondobject contributes to correction for curvature of field and coma, andthe rear lens (L_(2R)) of the negative meniscus shape disposed asclosest to the second object in the second lens group (G₂) and shapedwith the concave surface to the first object contributes mainly tocorrection for coma. The rear lens (L_(2R)) also contributes tocorrection for curvature of field. Further, in the intermediate lensgroup (G_(2M)) disposed between the front lens (L_(2F)) and the rearlens (L_(2R)), the first lens (L_(M1)) with the positive refractingpower contributes to correction for negative distortion generated by thesecond lens (L_(M2)) and third lens (L_(M3)) of the negative refractingpowers greatly contributing to correction for curvature of field.

Condition (1) defines an optimum ratio between the focal length f₁ ofthe first lens group (G₁) with the positive refracting power and thedistance (object-to-image distance) L from the first object (reticleetc.) to the second object (wafer etc.). This condition (1) is mainlyfor well-balanced correction for distortion.

Above the upper limit of condition (1), large negative distortion willappear. In order to achieve a compact design as securing a reductionmagnification and a wide exposure area and to achieve good correctionfor distortion, the upper limit of condition (1) is preferably set to0.14, as f₁ /L<0.14. In order to suppress appearance of sphericalaberration of pupil, the lower limit of condition (1) is preferably setto 0.02, as 0.02<f₁ /L.

Condition (2) defines an optimum ratio between the focal length f₂ ofthe second lens group (G₂) with the negative refracting power and thedistance (object-to-image distance) L from the first object (reticleetc.) to the second object (wafer etc.). This condition (2) is acondition for achieving a compact design as securing a wide exposureregion and achieving good correction for Petzval sum.

Here, below the lower limit of condition (2), it becomes difficult toachieve the compact design as securing the wide exposure region andpositive Petzval sum will appear, thus not preferred. In order toachieve further compact design or superior correction for Petzval sum,the lower limit of condition (2) is preferably set to -0.032, as-0.032<f₂ /L. In order to suppress appearance of negative distortion,the upper limit of condition (2) is preferably set to -0.005, as f₂/L<-0.005.

Condition (3) defines an optimum ratio between the focal length f₃ ofthe third lens group (G₃) with the positive refracting power and thedistance (object-to-image distance) L from the first object (reticleetc.) to the second object (wafer etc.). Here, below the lower limit ofcondition (3), the refractive power of the second lens group (G₂) or thefourth lens group (G₄) becomes too strong, resulting in giving rise tonegative distortion and coma in the second lens group (G₂) or givingrise to coma in the fourth lens group (G₄). On the other hand, above theupper limit of condition (3), the refractive power of the second lensgroup (G₂) or the fourth lens group (G₄) becomes too weak, failing towell correct Petzval sum.

Condition (4) defines an optimum ratio between the focal length f₄ ofthe fourth lens group (G₄) with the negative refracting power and thedistance (object-to-image distance) L from the first object (reticleetc.) to the second object (wafer etc.).

Here, above the upper limit of condition (4), coma will appear, thus notpreferred. Further, in order to suppress appearance of coma, the upperlimit of condition (4) is preferably set to -0.047, as f₄ /L<-0.047.

In order to well correct spherical aberration, the lower limit ofcondition (4) is preferably set to -0.098, as -0.098<f₄ /L.

Condition (5) defines an optimum ratio between the focal length f₅ ofthe fifth lens group (G₅) with the positive refracting power and thedistance (object-to-image distance) L from the first object (reticleetc.) to the second object (wafer etc.). This condition (5) is forachieving well-balanced correction for spherical aberration, distortion,and Petzval sum as maintaining a large numerical aperture. Below thelower limit of this condition (5), the refracting power of the fifthlens group (G₅) becomes too strong, resulting in giving rise to greatnegative spherical aberration in addition to negative distortion in thefifth lens group (G₅). Above the upper limit of this condition (5), therefracting power of the fifth lens group (G₅) becomes too weak, whichinevitably weakens the refracting power of the fourth lens group (G₄)with the negative refracting power. As a consequence, Petzval sum willnot be well corrected.

Condition (6) defines an optimum ratio between the focal length f₆ ofthe sixth lens group (G₆) with the positive refracting power and thedistance (object-to-image distance) L from the first object (reticleetc.) to the second object (wafer etc.). This condition (6) is forsuppressing appearance of higher-order spherical aberration and negativedistortion as maintaining a large numerical aperture. Below the lowerlimit of this condition (6), the sixth lens group (G₆) itself gives riseto great negative distortion; above the upper limit of this condition(6), higher-order spherical aberration will appear.

On the basis of the above composition it is preferred that when I is anaxial distance from the first object to a first-object-side focal pointF of the entire projection optical system and L is the distance from thefirst object to the second object, the following condition be satisfied:

    1.0<I/L.                                                   (7)

The condition (7) defines an optimum ratio between the axial distance Ifrom the first object to the first-object-side focal point F of theentire projection optical system and the distance (object-imagedistance) L from the first object (reticle etc.) to the second object(wafer etc.). Here, the first-object-side focal point F of the entireprojection optical system means an intersecting point of outgoing lightfrom the projection optical system with the optical axis aftercollimated light beams are let to enter the projection optical system onthe second object side in the paraxial region with respect to theoptical axis of the projection optical system and when the light beamsin the paraxial region are outgoing from the projection optical system.

Below the lower limit of this condition (7) the first-object-sidetelecentricity of the projection optical system will become considerablydestroyed, so that changes of magnification and distortion due to anaxial deviation of the first object will become large. As a result, itbecomes difficult to faithfully project an image of the first object ata desired magnification onto the second object. In order to fullysuppress the changes of magnification and distortion due to the axialdeviation of the first object, the lower limit of the above condition(7) is preferably set to 1.7, i.e., 1.7<I/L. Further, in order tocorrect a spherical aberration and a distortion of the pupil both in agood balance while maintaining the compact design of the projectionoptical system, the upper limit of the above condition (7) is preferablyset to 6.8, i.e., I/L<6.8.

It is also preferred that the fourth lens group (G₄) have a front lensgroup disposed as closest to the first object and a rear lens groupdisposed as closest to the second object, that an intermediate lensgroup having a first negative lens (L₄₃) and a second negative lens(L₄₄) in order from the side of the first object be disposed between thefront lens group in the fourth lens group (G₄) and the rear lens groupin the fourth lens group (G₄), that the front lens group have twonegative meniscus lenses (L₄₁, L₄₂) each shaped with a concave surfaceto the second object, that the rear lens group has a negative lens (L₄₆)with a concave surface to the first object, and that when f_(4A) is afocal length of the first negative lens (L₄₃) in the fourth lens group(G₄) and f_(4B) is a focal length of the second negative lens (L₄₄) inthe fourth lens group (G₄), the following condition be satisfied:

    0.05<f.sub.4A /f.sub.4B <20.                               (8)

Below the lower limit of condition (8), the refractive power of thefirst negative lens (L₄₃) becomes strong relative to the refractivepower of the second negative lens (L₄₄), so that the first negative lens(L₄₃) will give rise to higher-order spherical aberration andhigher-order coma. In order to suppress appearance of the higher-orderspherical aberration and higher-order coma, the lower limit of the abovecondition (8) is preferably set to 0.1, as 0.1<f_(4A) /f_(4B). On theother hand, above the upper limit of condition (8), the refracting powerof the second negative lens (L₄₄) becomes strong relative to therefracting power of the first negative lens (L₄₃), so that the secondnegative lens (L₄₄) will give rise to higher-order spherical aberrationand higher-order coma. In order to further suppress appearance ofhigher-order spherical aberration and higher-order coma, the upper limitof the above condition (8) is preferably set to 10, as f_(4A) /f_(4B)<10.

It is also preferred that when r_(2Ff) is a radius of curvature of afirst-object-side surface of the front lens (L₂ F) and r_(2Fr) is aradius of curvature of a second-object-side surface of the front lens(L_(2F)), the front lens (L_(2F)) in the second lens group (G₂) satisfythe following condition:

    1.00≦(r.sub.2Ff -r.sub.2Fr)/(r.sub.2Ff +r.sub.2Fr)<5.0.(9)

Below the lower limit of this condition (9), sufficient correction forspherical aberration of pupil becomes impossible, thus not preferred. Onthe other hand, above the upper limit of this condition (9), coma willappear, thus not preferred.

It is also preferred that the fourth lens group (G₄) have a front lensgroup having a negative lens (L₄₁) disposed as closest to the firstobject and shaped with a concave surface to the second object, and arear lens group having a negative lens (L₄₆) disposed as closest to thesecond object and shaped with a concave surface to the first object,that an intermediate lens group having at least a negative lens (L₄₄)and a positive lens (L₄₅) with a convex surface adjacent to a concavesurface of the negative lens (L₄₄) be disposed between the front lensgroup in the fourth lens group (G₄) and the rear lens group in thefourth lens group (G₄), and that when r_(4N) is a radius of curvature ofthe concave surface of the negative lens (L₄₄) in the intermediate lensgroup and r_(4P) is a radius of curvature of the convex surface of thepositive lens (L₄₅) in the intermediate lens group, the followingcondition be satisfied:

    -0.9<(r.sub.4N -r.sub.4P)/(r.sub.4N +r.sub.4P)<0.9,        (10)

provided that when L is the distance from the first object to the secondobject, the concave surface of the negative lens (L₄₄) in theintermediate lens group or the convex surface of the positive lens (L₄₅)in the intermediate lens group satisfies at least one of the followingconditions:

    |r.sub.4N /L|<2.0                        (11)

    |r.sub.4P /L|<2.0.                       (12)

Conditions (10) to (12) define an optimum configuration of a gas lensformed by the concave surface of the negative lens (L₄₄) in theintermediate lens group and the convex surface of the positive lens(L₄₅) in the intermediate lens group. When condition (11) or (12) issatisfied, this gas lens can correct higher-order spherical aberration.For further correction of higher-order spherical aberration, the upperlimits of condition (11) and condition (12) are preferably set to 0.8,as |r_(4N) /L|<0.8 and |r_(4P) /L|<0.8. Here, above the upper limit orbelow the lower limit of condition (10), coma will appear, thus notpreferred. If neither condition (11) nor condition (12) is satisfied,correction for higher-order spherical aberration is impossible even ifcondition (10) is satisfied, thus not preferred.

It is also preferred that when f₂₂ is a focal length of the second lens(L_(M2)) with the negative refracting power in the second lens group(G₂) and f₂₃ is a focal length of the third lens (L_(M3)) with thenegative refracting power in the second lens group (G₂), the followingcondition be satisfied:

    0.1<f.sub.22 /f.sub.23 <10.                                (13)

Below the lower limit of the condition (13) the refracting power of thesecond negative lens (L_(M2)) becomes strong relative to the refractingpower of the third negative lens (L_(M3)), so that the second negativelens (L_(M2)) generates a large coma and a large negative distortion. Inorder to correct the negative distortion in a better balance, the lowerlimit of the above condition (13) is preferably set to 0.7, i.e.,0.7<f₂₂ /f₂₃. Above the upper limit of this condition (13) therefracting power of the third negative lens (L_(M3)) becomes strongrelative to the refracting power of the second negative lens (L_(M2)),so that the third negative lens generates a large coma and a largenegative distortion. In order to correct the negative distortion in abetter balance while well correcting the coma, the upper limit of theabove condition (13) is preferably set to 1.5, i.e., f₂₄ /f₂₃ <1.5.

It is also preferred that the fifth lens group (G₅) have a negativemeniscus lens (for example, L₅₄), and a positive lens (for example, L₅₃)disposed as adjacent to a concave surface of the negative meniscus lensand having a convex surface opposed to the concave surface of thenegative meniscus lens and that when r_(5n) is a radius of curvature ofthe concave surface of the negative meniscus lens in the fifth lensgroup (G₅) and r_(5P) is a radius of curvature of the convex surface,opposed to the concave surface of the negative meniscus lens, of thepositive lens disposed as adjacent to the concave surface of thenegative meniscus lens in the fifth lens group (G₅), the followingcondition be satisfied:

    0<(r.sub.5P -r.sub.5n)/(r.sub.5P +r.sub.5n)<1.             (14)

In this case, it is preferred that the negative meniscus lens (forexample, L₅₄) and the positive lens (L₅₃) adjacent to the concavesurface of the negative meniscus lens be disposed between at least onepositive lens (for example, L₅₂) in the fifth lens group G₅ and at leastone positive lens (for example, L₅₅) in the fifth lens group (G₅).

In this case, in order to suppress the negative distortion withoutgenerating the higher-order spherical aberrations in the lens (L₆₁)located closest to the first object in the sixth lens group (G₆), it isdesirable that the lens surface closest to the first object have a shapewith a convex surface to the first object and that the followingcondition be satisfied when a radius of curvature on the second objectside, of the negative lens (L₅₈) placed as closest to the second objectin the fifth lens group (G₅) is r_(5R) and a radius of curvature on thefirst object side, of the lens (L₆₁) placed as closest to the firstobject in the sixth lens group (G₆) is r_(6F).

    -0.90<(r.sub.5R -r.sub.6F)/(r.sub.5R +r.sub.6F)<-0.001     (15)

This condition (15) defines an optimum shape of a gas lens formedbetween the fifth lens group (G₅) and the sixth lens group (G₆). Belowthe lower limit of this condition (15) a curvature of thesecond-object-side concave surface of the negative lens (L₅₈) locatedclosest to the second object in the fifth lens group (G₅) becomes toostrong, thereby generating higher-order comas. Above the upper limit ofthis condition (15) refracting power of the gas lens itself formedbetween the fifth lens group (G₅) and the sixth lens group (G₆) becomesweak, so that a quantity of the positive distortion generated by thisgas lens becomes small, which makes it difficult to well correct anegative distortion generated by the positive lens in the fifth lensgroup (G₅). In order to fully suppress the generation of higher-ordercomas, the lower limit of the above condition (15) is preferably set to-0.30, i.e., -0.30<(r_(5R) -r_(6F))/(r_(5R) +r_(6F)).

Also, it is further preferable that the following condition be satisfiedwhen a lens group separation between the fifth lens group (G₅) and thesixth lens group (G₆) is d₅₆ and the distance from the first object tothe second object is L.

    d.sub.56 /L<0.017                                          (16)

Above the upper limit of this condition (16), the lens group separationbetween the fifth lens group (G₅) and the sixth lens group (G₆) becomestoo large, so that a quantity of the positive distortion generatedbecomes small. As a result, it becomes difficult to correct the negativedistortion generated by the positive lens in the fifth lens group (G₅)in a good balance.

Also, it is more preferable that the following condition be satisfiedwhen a radius of curvature of the lens surface closest to the firstobject in the sixth lens group (G₆) is r_(6F) and an axial distance fromthe lens surface closest to the first object in the sixth lens group(G₆) to the second object is d₆.

    0.50<d.sub.6 /r.sub.6F <1.50                               (17)

Below the lower limit of this condition (17), the positive refractingpower of the lens surface closest to the first object in the sixth lensgroup (G₆) becomes too strong, so that a large negative distortion and alarge coma are generated. Above the upper limit of this condition (17),the positive refracting power of the lens surface closest to the firstobject in the sixth lens group (G₆) becomes too weak, thus generating alarge coma. In order to further suppress the generation of coma, thelower limit of the condition (17) is preferably set to 0.84, i.e.,0.84<d₆ /r₆ F.

Also, it is to be more desired that said fifth lens group (G₅) have anegative lens (L₅₈) placed as closest to the second object and having aconcave surface opposed to the second object and that the followingcondition be satisfied when a radius of curvature on the first objectside in the negative lens (L₅₈) closest to the second object in saidfifth lens group (G₅) is r_(5F) and a radius of curvature on the secondobject side in the negative lens (L₅₈) closest to the second object insaid fifth lens group (G₅) is r_(5R) :

    0.30<(r.sub.5F -r.sub.5R)/(r.sub.5F +r.sub.5R)<1.28.       (18)

Below the lower limit of this condition (18), it becomes difficult tocorrect both the Petzval sum and the coma; above the upper limit of thiscondition (18), large higher-order comas appear, which is notpreferable. In order to further prevent the generation of higher-ordercomas, the upper limit of the condition (18) is preferably set to 0.93,i.e., (r_(5F) -r_(5R))/(r_(5F) +r_(5R))<0.93.

It is more desired that when f₂₁ is a focal length of the first lens(L_(M1)) with the positive refracting power in the intermediate lensgroup (G_(2M)) in the second lens group (G₂) and L is the distance fromthe first object to the second object, the following condition besatisfied:

    0.230<f.sub.21 /L<0.40.                                    (19)

Below the lower limit of condition (19), positive distortion willappear; above the upper limit of condition (19), negative distortionwill appear, either of which is thus not preferred. Further, in order tofurther correct the negative distortion, the second-object-side lenssurface of the first lens (L_(M1)) is preferably formed in a lensconfiguration shaped with a convex surface facing the second object.

It is also preferred that when f_(2F) is a focal length of the frontlens (L_(2F)) with the negative refracting power disposed as closest tothe first object in the second lens group (G₂) and shaped with theconcave surface to the second object and f_(2R) is a focal length of therear lens (L_(2R)) with the negative refracting power disposed asclosest to the second object in the second lens group (G₂) and shapedwith the concave surface to the first object, the following condition besatisfied:

    0≦f.sub.2F /f.sub.2R <18.                           (20)

Also, the front lens (L_(2F)) and the rear lens (L_(2R)) in the secondlens group (G₂) preferably satisfy the following condition when thefocal length of the front lens (L_(2F)) placed as closest to the firstobject in the second lens group (G₂) and having the negative refractingpower with a concave surface to the second object is f_(2F) and thefocal length of the rear lens (L_(2R)) placed as closest to the secondobject in the second lens group (G₂) and having the negative refractingpower with a concave surface to the second object is f_(2R).

    0≦f.sub.2F /f.sub.2R <18                            (20)

The condition (20) defines an optimum ratio between the focal lengthf_(2R) of the rear lens (L_(2R)) in the second lens group (G₂) and thefocal length f_(2F) of the front lens (L_(2F)) in the second lens group(G₂). Below the lower limit and above the upper limit of this condition(20), a balance is destroyed for refracting power of the first lensgroup (G₁) or the third lens group (G₃), which makes it difficult tocorrect the distortion well or to correct the Petzval sum and theastigmatism simultaneously well.

In order to further well correct Petzval sum, the intermediate lensgroup (G_(2M)) in the second lens group (G₂) preferably has a negativerefracting power.

For the above lens groups to achieve satisfactory aberration correctionfunctions, specifically, they are desired to be constructed in thefollowing arrangements.

First, for the first lens group (G₁) to have a function to suppressappearance of higher-order distortion and appearance of sphericalaberration of pupil, the first lens group (G₁) preferably has at leasttwo positive lenses; for the third lens group (G₃) to have a function tosuppress degradation of spherical aberration and Petzval sum, the thirdlens group (G₃) preferably has at least three positive lenses; further,for the fourth lens group (G₄) to have a function to suppress appearanceof coma as correcting Petzval sum, the fourth lens group (G₄) preferablyhas at least three negative lenses. For the fifth lens group (G₅) tohave a function to suppress appearance of negative distortion andspherical aberration, the fifth lens group (G₅) preferably has at leastfive positive lenses; further, for the fifth lens group (G₅) to have afunction to correct negative distortion and Petzval sum, the fifth lensgroup (G₅) preferably has at least one negative lens. For the sixth lensgroup (G₆) to effect focus on the second object so as not to give riseto large spherical aberration, the sixth lens group (G₆) preferably hasat least one positive lens.

For further compact design, the intermediate lens group in the secondlens group desirably comprises only two negative lenses.

For the sixth lens group (G₆) to have a function to further suppressappearance of negative distortion, the sixth lens group (G₆) ispreferably arranged to comprise three or less lenses including at leastone lens surface satisfying the following condition (21).

    1/|ΦL|<20                            (21)

where

Φ: a refractive power of the lens surface; and

L: the distance (object-to-image distance) from the first object to thesecond object.

The refractive power of lens surface, stated here, is given by thefollowing equation where r is a radius of curvature of the lens surface,n₁ a refractive index of a medium on the first object side of the lenssurface, and n₂ a refractive index of a medium on the second object sideof the lens surface.

    Φ=(n.sub.2 -n.sub.1)/r

Here, if there are four or more lenses having the lens surfacesatisfying this condition (21), the number of lens surfaces with somecurvature, located near the second object, becomes increased, whichgenerates the distortion, thus not preferable.

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not to beconsidered as limiting the present invention.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art form this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing to show parameters defined in embodiments of thepresent invention.

FIG. 2 is a drawing to show schematic structure of an exposure apparatusto which the projection optical system according to the presentinvention is applied.

FIG. 3 is a lens arrangement drawing of the projection optical system inthe first embodiment according to the present invention.

FIG. 4 is a lens arrangement drawing of the projection optical system inthe second embodiment according to the present invention.

FIG. 5 is a lens arrangement drawing of the projection optical system inthe third embodiment according to the present invention.

FIG. 6 is a lens arrangement drawing of the projection optical system inthe fourth embodiment according to the present invention.

FIGS. 7-10 are aberration diagrams to show aberrations in the projectionoptical system of the first embodiment.

FIGS. 11-14 are aberration diagrams to show aberrations in theprojection optical system of the second embodiment.

FIGS. 15-18 are aberration diagrams to show aberrations in theprojection optical system of the third embodiment.

FIGS. 19-22 are aberration diagrams to show aberrations in theprojection optical system of the fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the projection optical system according to thepresent invention will be described with reference to the drawings. Inthe examples, the present invention is applied to the projection opticalsystem in the projection exposure apparatus for projecting an image ofpatterns of reticle onto a wafer coated with a photoresist. FIG. 2 showsa basic structure of the exposure apparatus according to the presentinvention. As shown in FIG. 2, an exposure apparatus of the presentinvention comprises at least a wafer stage 3 allowing a photosensitivesubstrate W to be held on a main surface 3a thereof, an illuminationoptical system 1 for emitting exposure light of a predeterminedwavelength and transferring a predetermined pattern of a mask (reticleR) onto the substrate W, a light source 100 for supplying an exposurelight to the illumination optical system 1, a projection optical system5 provided between a first surface P1 (object plane) on which the mask Ris disposed and a second surface P2 (image plane) to which a surface ofthe substrate W is corresponded, for projecting an image of the patternof the mask R onto the substrate W. The illumination optical system 1includes an alignment optical system 110 for adjusting a relativepositions between the mask R and the wafer W, and the mask R is disposedon a reticle stage 2 which is movable in parallel with respect to themain surface of the wafer stage 3. A reticle exchange system 200 conveysand changes a reticle (mask R) to be set on the reticle stage 2. Thereticle exchange system 200 includes a stage driver for moving thereticle stage 2 in parallel with respect to the main surface 3a of thewafer stage 3. The projection optical system 5 has a space permitting anaperture stop 6 to be set therein. The sensitive substrate W comprises awafer 8 such as a silicon wafer or a glass plate, etc., and aphotosensitive material 7 such as a photoresist or the like coating asurface of the wafer 8. The wafer stage 3 is moved in parallel withrespect to a object plane P1 by a stage control system 300. Further,since a main control section 400 such as a computer system controls thelight source 100, the reticle exchange system 200, the stage controlsystem 300 or the like, the exposure apparatus can perform a harmoniousaction as a whole.

The techniques relating to an exposure apparatus of the presentinvention are described, for example, in U.S. patent applications Ser.Nos. 255,927, 260,398, 299,305, U.S. Pat. Nos. 4,497,015, 4,666,273,5,194,893, 5,253,110, 5,333,035, 5,365,051, 5,379,091, or the like. Thereference of U.S. patent application Ser. No. 255,927 teaches anillumination optical system (using a laser source) applied to a scantype exposure apparatus. The reference of U.S. patent application Ser.No. 260,398 teaches an illumination optical system (using a lamp source)applied to a scan type exposure apparatus. The reference of U.S. patentapplication Ser. No. 299,305 teaches an alignment optical system appliedto a scan type exposure apparatus. The reference of U.S. Pat. No.4,497,015 teaches an illumination optical system (using a lamp source)applied to a scan type exposure apparatus. The reference of U.S. Pat.No. 4,666,273 teaches a step-and repeat type exposure apparatus capableof using the projection optical system of the present invention. Thereference of U.S. Pat. No. 5,194,893 teaches an illumination opticalsystem, an illumination region, mask-side and reticle-sideinterferometers, a focusing optical system, alignment optical system, orthe like. The reference of U.S. Pat. No. 5,253,110 teaches anillumination optical system (using a laser source) applied to astep-and-repeat type exposure apparatus. The '110 reference can beapplied to a scan type exposure apparatus. The reference of U.S. Pat.No. 5,333,035 teaches an application of an illumination optical systemapplied to an exposure apparatus. The reference of U.S. Pat. No.5,365,051 teaches a auto-focusing system applied to an exposureapparatus. The reference of U.S. Pat. No. 5,379,091 teaches anillumination optical system (using a laser source) applied to a scantype exposure apparatus.

As described above, a reticle R (first object) as a projection mask withspecific circuit patterns formed therein is disposed on the object plane(P1) of the projection optical system 1 and a wafer W (second object) asa substrate on the image plane (P2) of the projection optical system 1.Here, the reticle R is held on a reticle stage 2 and the wafer W on awafer stage 3 arranged as movable on a two-dimensional basis. Disposedabove the reticle R is an illumination optical system 1 for uniformlyilluminating the reticle R.

In the above arrangement, light supplied from the light source 100through the illumination optical system 1 illuminates the reticle R toform an image at the pupil position of the projection optical system 1(the position of aperture stop 6). Namely, the illumination opticalsystem 1 uniformly illuminates the reticle R under Kohler illumination.Then the pattern image of reticle R illuminated under Kohlerillumination is projected (or transferred) onto the wafer W.

The present embodiment shows an example of which the light source 100 isa mercury lamp for supplying the i-line (365 nm). The structure of theprojection optical system in each embodiment will be described byreference to FIG. 3 to FIG. 6. FIG. 3 to FIG. 6 are lens structuraldrawings of the projection optical systems 1 in the first to fourthembodiments, respectively, according to the present invention.

As shown in FIG. 3 to FIG. 6, the projection optical system 1 in eachembodiment has a first lens group G₁ with a positive refractive power, asecond lens group G₂ with a negative refractive power, a third lensgroup G₃ with a positive refractive power, a fourth lens group G₄ with anegative refractive power, a fifth lens group G₅ with a positiverefractive power, and a sixth lens unit G₆ with a positive refractivepower in order from the side of reticle R as a first object, is arrangedas substantially telecentric on the object side (reticle R side) and onthe image side (wafer W side), and has a reduction magnification.

In the projection optical system 1 in each of the embodiments shown inFIG. 3 to FIG. 6, an object-to-image distance (a distance along theoptical axis from the object plane to the image plane, or a distancealong the optical axis from the reticle R to wafer W) L is 1100, animage-side numerical aperture NA is 0.57, a projection magnification βis 1/5, and a diameter of an exposure area on the wafer W is 31.2. Theobject-to-image distance L and the diameter of the exposure area areexpressed in a same unit, and the unit corresponds to a unit of r and dshown in the following tables 1, 3, 5 and 7.

First described is a specific lens arrangement of the first embodimentshown in FIG. 3. The first lens group G₁ has a negative meniscus lensL₁₁ shaped with a concave surface to the image, a positive lens(positive lens of a biconvex shape) L₁₂ shaped with a convex surface tothe object, and two positive lenses (positive lenses of biconvex shapes)L₁₃, L₁₄ each shaped with a strong-curvature surface to the object inorder from the object side.

Further, the second lens group G₂ has a negative lens (negative lens ofa biconcave shape: front lens) L_(2F) disposed as closest to the objectand shaped with a concave surface to the image, a negative meniscus lens(rear lens) L_(2R) disposed as closest to the image and shaped with aconcave surface to the object, and an intermediate lens group G_(2M)with a negative refractive power disposed between these negative lensL_(2F) and negative lens L_(2R). This intermediate lens group G_(2M) hasa positive lens (positive lens of a biconvex shape: first lens) L_(M1)shaped with a strong-curvature surface to the image, a negative lens(negative lens of a biconcave shape: second lens) L_(M2) shaped with astrong-curvature surface to the image, and a negative lens (negativelens of a biconcave shape: third lens) L_(M3) shaped with astrong-curvature surface to the object in order from the object side.

The third lens group G₃ has two positive lenses (positive meniscuslenses) L₃₁, L₃₂ each shaped with a strong-curvature surface to theimage, a positive lens L₃₃ of a biconvex shape, a positive lens(positive lens of a biconvex shape) L₃₄ shaped with a strong-curvaturesurface to the object, and a positive lens (positive meniscus lens) L₃₅shaped with a strong-curvature surface to the object in order from theobject side.

The fourth lens group G₄ has two negative meniscus lenses (front lensgroup) L₄₁, L₄₂ each shaped with a concave surface to the image, anegative lens (negative meniscus lens: first negative lens) L₄₃ shapedwith a concave surface to the object, a negative lens (second negativelens: negative lens with a concave surface to the image) L₄₄ of abiconcave shape, a positive lens (positive meniscus lens: positive lenshaving a convex surface adjacent to the concave surface of the negativelens L₄₄) L₄₅ shaped with a convex surface to the object, and a negativelens (negative lens of a biconcave shape: rear lens group) L₄₆ shapedwith a concave surface to the object in order from the object side.

The fifth lens group G₅ has two positive lenses (positive lenses ofbiconvex shapes) L₅₁, L₅₂ each shaped with a convex surface to theimage, a positive lens L₅₃ of a biconvex shape, a negative meniscus lensL₅₄ shaped with a concave surface to the object, a positive lens L₅₅shaped with a stronger-curvature surface to the object, two positivelenses (positive meniscus lenses) L₅₆, L₅₇ each shaped with astronger-curvature surface to the object, and a negative meniscus lensL₅₈ shaped with a concave surface to the image in order from the objectside.

Further, the sixth lens group G₆ is composed of a positive lens(positive lens of a biconvex shape) L₆₁ shaped with a stronger-curvaturesurface to the object, and a negative lens (negative lens of a biconcaveshape) L₆₂ shaped with a concave surface to the object in order from theobject side.

In the present embodiment, an aperture stop 6 is disposed between thepositive meniscus lens L₄₅ with the convex surface to the object and thenegative lens L₄₆ of the biconcave shape, that is, between theintermediate lens group in the fourth lens group G₄ and the rear lensgroup in the fourth lens group G₄.

In the first lens group G₁ in the present embodiment, the concavesurface of the negative meniscus lens L₁₁ with the concave surface tothe image and the object-side lens surface of the positive biconvex lensL₁₂ have nearly equal curvatures and are arranged as relatively close toeach other, and these two lens surfaces correct higher-order distortion.

Since the first lens L_(M1) with the positive refractive power in thesecond lens group G_(2M) is constructed in the biconvex shape with theconvex surface to the image and also with the other convex surface tothe object, it can suppress appearance of spherical aberration of pupil.

Since the fourth lens group G₄ is so arranged that the negative meniscuslens L₄₁ with the concave surface to the image is disposed on the objectside of the negative lens (negative biconcave lens) L₄₄ and that thenegative lens L₄₆ with the concave surface to the object is disposed onthe image side of the negative lens (negative biconcave lens) L₄₄, itcan correct Petzval sum as suppressing appearance of coma.

Since in the first embodiment the aperture stop 6 is placed between theimage-side concave surface of the negative meniscus lens L₄₁ and theobject-side concave surface of the negative lens L₄₆ in the fourth lensgroup G₄, the lens groups of from the third lend group G₃ to the sixthlens group G₆ can be arranged around the aperture stop 6 with a more orless reduction magnification and without destroying the symmetry toomuch, thus enabling to suppress asymmetric aberration, particularly comaand distortion. Since the positive lens L₅₃ in the fifth lens group G₅has a convex surface opposed to the negative meniscus lens L₅₄ and theother lens surface on the opposite side to the negative meniscus lensL₅₄ is also a convex surface, higher-order spherical aberration can beprevented from appearing with an increase of numerical aperture.

The specific lens arrangement of the second embodiment shown in FIG. 4is similar to that of the first embodiment as shown in FIG. 3 anddescribed above. The third lens group G₃ in the second embodiment isdifferent from that in the first embodiment in that the third lens groupG₃ is composed of two positive lenses (positive meniscus lenses) L₃₁,L₃₂ each shaped with a strong-curvature surface to the image, a positivelens L₃₃ of a biconvex shape, a positive lens (positive lens of abiconvex shape) L₃₄ shaped with a strong-curvature surface to theobject, and a positive lens (positive lens of a biconvex shape) L₃₅shaped with a strong-curvature surface to the object in order from theobject side.

In the second embodiment, the fourth lens group G₄ is different fromthat in the first embodiment in that the fourth lens group G₄ iscomposed of two negative meniscus lenses (front lens group) L₄₁, L₄₂each shaped with a concave surface to the image, a negative lens(negative lens of a biconcave shape: first negative lens) L₄₃ shapedwith a concave surface to the object, a negative lens (second negativelens: negative lens with a concave surface to the image) L₄₄ of abiconcave shape, a positive lens (positive meniscus lens: positive lenshaving a convex surface adjacent to the concave surface of the negativelens L₄₄) L₄₅ shaped with a convex surface to the object, and a negativelens (negative lens of a biconcave shape: rear lens group) L₄₆ shapedwith a stronger concave surface to the object in order from the objectside, but the function thereof is the same as that in the firstembodiment as described above.

Further, the first and second lens groups G₁, G₂ and the fifth and sixthlens groups G₅, G₆ in the second embodiment achieve the same functionsas those in the first embodiment as described above.

The specific lens arrangement of the third embodiment shown in FIG. 5 issimilar to that of the first embodiment shown in FIG. 3 and describedpreviously. The first lens group G₁ of the present embodiment isdifferent from that of the first embodiment in that the first lens groupG₁ is composed of a negative meniscus lens L₁₁ shaped with a concavesurface to the image, a positive lens (positive lens of a biconvexshape) L₁₂ shaped with a convex surface to the object, a positive lens(positive lens of a plano-convex shape) L₁₃ shaped with astrong-curvature surface to the object, and a positive lens (positivelens of a biconvex shape) L₁₄ shaped with a strong-curvature surface tothe object in order from the object side, but the function thereof isthe same as that in the first embodiment as described previously.

The second to sixth lens groups G₂ -G₆ in the third embodiment achievethe same functions as those in the first embodiment as describedpreviously.

The specific lens arrangement of the fourth embodiment of FIG. 6 issimilar to that of the first embodiment shown in FIG. 3 and describedpreviously. The fourth lens group G₄ in the present embodiment isdifferent from that of the first embodiment in that the fourth lensgroup G₄ is composed of two negative meniscus lenses (front lens group)L₄₁, L₄₂ each with a concave surface to the image, a negative lens(negative lens of a biconcave shape: first negative lens) L₄₃ shapedwith a concave surface to the object, a negative lens (second negativelens: negative lens with a concave surface to the image) L₄₄ of abiconcave shape, a positive lens (positive meniscus lens: a positivelens having a convex surface adjacent to the concave surface of thenegative lens L₄₄) L₄₅ shaped with a convex surface to the object, and anegative lens (negative lens of a biconcave shape: rear lens group) L₄₆shaped with a concave surface to the object in order from the objectside, but the function thereof is the same as that in the firstembodiment as described previously.

Further, in the fourth embodiment, the sixth lens group G₆ is differentfrom that of the first embodiment in that the sixth lens group G₆ iscomposed of a positive lens (positive lens of a biconvex shape) L₆₁shaped with a stronger-curvature surface to the object and a negativelens (negative meniscus lens) L₆₂ shaped with a concave surface to theobject in order from the object side.

The first to third lens groups G₁ to G₃ and the fifth lens group G₅ inthe present embodiment achieve the same functions as those in the firstembodiment described previously.

Table 1 to Table 8 to follow list values of specifications andcorrespondent values to the conditions for the respective embodiments inthe present invention.

In the tables, left-end numerals represent orders from the object side(reticle R side), r radii of curvatures of lens surfaces, d separationsbetween lens surfaces, n refractive indices of glass materials forexposure wavelength λ of 365 nm, d₀ the distance along the optical axisfrom the first object (reticle R) to the lens surface (first lenssurface) closest to the object (reticle R) in the first lens group G₁, βthe projection magnification of projection optical system, Bf thedistance along the optical axis from the lens surface closest to theimage (wafer W) in the sixth lens group G₆ to the image plane P2 (waferW plane), NA the numerical aperture on the image side (wafer W side), ofprojection optical system, and L is the object-to-image distance fromthe object plane P1 (reticle R plane) to the image plane P2 (wafer Wplane). Further, in the tables, f₁ represents the focal length of thefirst lens group G₁, f₂ the focal length of the second lens group G₂, f₃the focal length of the third lens group G₃, f₄ the focal length of thefourth lens group G₄, f₅ the focal length of the fifth lens group G₅, f₆the focal length of the sixth lens group G₆, L the distance(object-to-image distance) from the object plane (reticle plane) to theimage plane (wafer plane), I the axial distance from the first object(reticle) to the first-object-side focal point F of the entireprojection optical system (provided that the first-object-side focalpoint F of the entire projection optical system means an intersectingpoint of emergent light with the optical axis when parallel light in theparaxial region with respect to the optical axis of the projectionoptical system is made incident from the second object side of theprojection optical system and the light in the paraxial region isemergent from the projection optical system), f_(4A) the focal length ofthe first negative lens (L₄₃) in the intermediate lens group in thefourth lens group G₄, f₄ the focal length of the second negative lens(L₄₄) in the intermediate lens group in the fourth lens group G₄,r_(2Ff) the radius of curvature of the first-object-side lens surface ofthe front lens L_(2F) in the second lens group G₂, R_(2Fr) the radius ofcurvature of the second-object-side lens surface of the front lensL_(2F) in the second lens group G₂, r_(4N) the radius of curvature ofthe second-object-side concave surface of the negative lens (L₄₄) in theintermediate lens group in the fourth lens group G₄, r_(4P) the radiusof curvature of the first-object-side convex surface of the positivelens (L₄₅) in the intermediate lens group in the fourth lens group G₄,f₂₂ the focal length of the second lens with the negative refractivepower in the second lens group, f₂₃ the focal length of the third lenswith the negative refractive power in the second lens group G₂, r_(5n)the radius of curvature of the concave surface in the negative meniscuslens in the fifth lens group G₅, r_(5p) the radius of curvature of theconvex surface opposed to the concave surface of the negative meniscuslens in the positive lens disposed as adjacent to the concave surface ofthe negative meniscus lens in the fifth lens group G₅, r_(5R) the radiusof curvature of the second-object-side surface of the negative lensdisposed as closest to the second object in the fifth lens group G₅,r_(6F) the radius of curvature of the first-object-side surface of thelens disposed as closest to the first object in the sixth lens group G₆,d₅₆ the lens group separation between the fifth lens group G₅ and thesixth lens group G₆, d₆ the axial distance from the lens surface closestto the first object in the sixth lens group G₆ to the second object,r_(5F) the radius of curvature of the first-object-side surface in thenegative lens disposed as closest to the second object in the fifth lensgroup G₅, f₂₁ the focal length of the first lens with the positiverefractive power in the intermediate lens group G_(2M) in the secondlens group G₂, f_(2F) the focal length of the front lens with thenegative refractive power disposed as closest to the first object in thesecond lens group G₂ and shaped with the concave surface to the secondobject, and f_(2R) the focal length of the rear lens of the negativemeniscus shape disposed as closest to the second object in the secondlens group G₂ and shaped with the concave surface to the object.

                  TABLE 1                                                         ______________________________________                                        First Embodiment                                                              dO = 94.97557                                                                 β= 1/5                                                                   NA = 0.57                                                                     Bf = 22.68864                                                                 L = 1100                                                                             r              d        n                                              1      758.59372      18.01962 1.66638                                        2      273.07409      8.00000                                                 3      407.25600      34.43806 1.53627                                        4      -305.98082     0.50000                                                 5      200.00000      36.31512 1.53627                                        6      -950.89920     0.50000                                                 7      251.35670      36.00000 1.53627                                        8      -1111.20100    5.00000                                                 9      -3000.00000    13.00000 1.66638                                        10     103.53326      19.34714                                                11     583.43731      21.86239 1.53627                                        12     -202.73262     3.71513                                                 13     -389.07550     13.00000 1.53627                                        14     118.39346      25.82991                                                15     -119.29984     13.00000 1.53627                                        16     228.68065      35.35939                                                17     -118.78231     15.61439 1.53627                                        18     -2000.00000    15.00000                                                19     -534.21970     30.58806 1.53627                                        20     -172.96367     0.50000                                                 21     -3045.95900    30.55054 1.53627                                        22     -252.31005     0.50000                                                 23     787.95642      31.33960 1.53627                                        24     -470.11486     0.50000                                                 25     429.05519      31.10739 1.53627                                        26     -1033.56100    0.50000                                                 27     276.54228      29.82671 1.53627                                        28     3383.80700     0.50000                                                 29     200.56082      25.00000 1.53627                                        30     149.82206      51.17799                                                31     191.38232      25.00000 1.53627                                        32     122.34204      25.15581                                                33     -276.65501     13.00000 1.66638                                        34     -597.90043     9.14516                                                 35     -190.18194     13.00000 1.66638                                        36     360.79756      3.75310                                                 37     434.45763      13.00000 1.53627                                        38     643.56408      31.17056                                                39     -951.39487     20.00000 1.66638                                        40     360.75541      3.46004                                                 41     395.41239      33.29191 1.53627                                        42     -229.24043     0.50000                                                 43     405.02177      21.76952 1.53627                                        44     -1456.27300    0.50000                                                 45     334.62149      34.87065 1.53627                                        46     -316.02886     8.19653                                                 47     -226.66975     20.00000 1.66638                                        48     -421.19119     0.50000                                                 49     245.00959      27.62592 1.53627                                        50     -6478.64400    0.50000                                                 51     118.64887      24.82664 1.53627                                        52     182.84804      0.50000                                                 53     106.97354      29.80517 1.53627                                        54     305.86346      2.86446                                                 55     330.12685      13.00000 1.66638                                        56     65.69252       7.67289                                                 57     76.63392       29.80077 1.53627                                        58     -405.45793     2.41289                                                 59     -314.04117     20.42250 1.53627                                        60     1180.34006     (Bf)                                                    ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Correspondent Values to the Conditions for First                              Embodiment                                                                    (1) f1 /L = 0.129                                                             (2) f2 /L = -0.0299                                                           (3) f3 /L = 0.106                                                             (4) f4 /L = -0.0697                                                           (5) f5 /L = 0.0804                                                            (6) f6 /L = 0.143                                                             (7) I/L = 2.02                                                                (8) f4A/f4B = 4.24                                                            (9) (r2Ff - r2Fr) / (r2Ff + r2Fr) = 1.07                                      (10) (r4N - r4P) / (r4N + r4PY) = -0.0926                                     (11) |r4N/L| = 0.328                                        (12) |r4P/L| = 0.395                                        (13) f22/f23 = 1.16                                                           (14) (r5p - r5n) / (r5p + r5n) = 0.165                                        (15) (r5R - r6F) / (r5R + r6F) = -0.0769                                      (16) d56/L = 0.00698                                                          (17) d6 / r6F = 0.983                                                         (18) (r5F - r5R) / (r5F + r5R) = 0.668                                        (19) f21/L = 0.258                                                            (20) f2F/f2R = 0.635                                                          ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Second Embodiment                                                             dO = 98.09086                                                                 β = 1/5                                                                  NA = 0.57                                                                     Bf = 22.68864                                                                 L = 1100                                                                             r              d        n                                              1      715.79825      18.01962 1.66638                                        2      257.11993      8.00000                                                 3      402.81202      34.43806 1.53627                                        4      -298.91362     0.50000                                                 5      200.00000      36.31512 1.53627                                        6      -811.20841     0.50000                                                 7      202.30081      36.00000 1.53627                                        8      -912.77876     -0.24598                                                9      -3000.00000    13.00000 1.66638                                        10     100.16757      19.34714                                                11     515.50992      21.86239 1.53627                                        12     -211.08983     3.71513                                                 13     -334.85048     13.00000 1.53627                                        14     119.28367      24.34073                                                15     -124.53825     13.00000 1.53627                                        16     196.56654      35.64064                                                17     -122.83913     15.61439 1.53627                                        18     -2000.00000    15.00000                                                19     -319.01403     30.58806 l.53627                                        20     -192.95790     0.50000                                                 21     -1320.53000    30.55054 1.53627                                        22     -229.09627     0.50000                                                 23     1670.41600     31.33960 1.53627                                        24     -355.67749     0.50000                                                 25     505.94351      31.10739 l.53627                                        26     -669.94239     0.50000                                                 27     272.78755      29.82671 1.53627                                        28     -11188.96200   0.50000                                                 29     205.32433      25.00000 1.53627                                        30     156.91075      68.35861                                                31     170.81860      25.00000 1.53627                                        32     119.41166      25.17539                                                33     -221.51521     13.00000 1.66638                                        34     3749.27900     7.91441                                                 35     -299.53056     13.00000 1.66638                                        36     360.79756      3.75310                                                 37     434.45763      13.00000 1.53627                                        38     643.56408      18.53967                                                39     -6417.33300    20.00000 1.66638                                        40     300.16308      3.46004                                                 41     329.77719      33.29191 1.53627                                        42     -264.12523     0.50000                                                 43     804.85248      21.76952 1.53627                                        44     -784.29788     0.50000                                                 45     273.73159      34.87065 1.53627                                        46     -325.58814     8.19653                                                 47     -214.52517     20.00000 1.66638                                        48     -405.91293     0.50000                                                 49     396.09997      27.62592 1.53627                                        50     -579.80514     0.50000                                                 51     115.71351      24.82664 1.53627                                        52     255.34580      0.50000                                                 53     104.86226      29.80517 1.53627                                        54     211.50003      2.86446                                                 55     312.25500      13.00000 1.66638                                        56     66.11566       7.67289                                                 57     76.78058       29.80077 1.53627                                        58     -437.18968     2.41289                                                 59     -324.32040     20.42250 1.53627                                        60     2434.44700     (Bf)                                                    ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Correspondent Values to the Conditions for Second                             Embodiment                                                                    (1) f1 /L = 0.119                                                             (2) f2 /L = -0.0292                                                           (3) f3 /L = 0.111                                                             (4) f4 /L = -0.0715                                                           (5) f5 /L = 0.0806                                                            (6) f6 /L = 0.140                                                             (7) I/L = 2.02                                                                (8) f4A/f4B = 1.29                                                            (9) (r2Ff - r2Fr) / (r2Ff + r2Fr) = 1.07                                      (10) (r4N - r4P) / (r4N + r4P) = -0.0926                                      (11) |r4N/L|= 0.328                                         (12) |r4P/L|= 0.395                                         (13) f22/f23 = 1.16                                                           (14) (r5p - r5n) / (rsp + r5n) = 0.206                                        (15) (r5R - r6F) / (r5R + r6F) = -0.114                                       (16) d56/L = 0.00698                                                          (17) d6 /r6F = 0.981                                                          (18) (r5F - r5R) / (r5F + r5R) = 0.673                                        (19) f21/L = 0.257                                                            (20) f2F/f2R = 0.593                                                          ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Third Embodiment                                                              dO = 105.97406                                                                β = 1/5                                                                  NA = 0.57                                                                     Bf = 21.09296                                                                 L = 1100                                                                             r              d        n                                              1      835.93450      19.00074 1.61298                                        2      349.00002      6.60188                                                 3      493.73823      30.01023 1.61536                                        4      -364.99999     1.12825                                                 5      189.67357      32.71424 1.61536                                        6      ∞        1.25667                                                 7      219.68925      26.27974 1.61536                                        8      -2935.50000    2.86486                                                 9      -1456.03000    15.60000 1.61298                                        10     98.87901       25.83515                                                11     572.77742      19.48735 1.48734                                        12     -245.99492     3.28431                                                 13     -517.01308     16.35209 1.61536                                        14     118.78195      22.95916                                                15     -151.83256     12.94478 1.61536                                        16     196.86505      33.74710                                                17     -129.25780     12.89677 1.61536                                        18     -491.95895     13.46314                                                19     -246.12435     22.58245 1.61536                                        20     -166.51997     0.39125                                                 21     -1477.30500    28.55306 1.61536                                        22     -216.04701     0.72991                                                 23     425.36937      33.51075 1.61536                                        24     -524.95999     0.96043                                                 25     438.35798      25.74084 1.48734                                        26     -1678.66000    0.33363                                                 27     292.51673      23.69782 1.48734                                        28     1518.72000     0.83738                                                 29     218.42396      26.38775 1.48734                                        30     148.35403      33.09868                                                31     203.95726      27.76454 1.61536                                        32     133.43801      30.67100                                                33     -211.86216     13.01538 1.61298                                        34     -1024.57000    15.53690                                                35     -160.75584     13.15020 1.61298                                        36     270.91502      0.55149                                                 37     250.92650      15.66663 1.48734                                        38     702.02996      23.07586                                                39     -827.25951     15.36200 1.61298                                        40     2298.00000     0.73901                                                 41     2301.62000     27.62162 1.48734                                        42     -223.08205     0.51051                                                 43     488.67440      34.23933 1.48734                                        44     -319.00802     0.49298                                                 45     500.98379      34.15684 1.61536                                        46     -369.12909     9.55181                                                 47     -242.59289     18.84686 1.61298                                        48     -613.52998     0.50392                                                 49     347.10206      30.00332 1.61536                                        50     -1728.40000    0.49017                                                 51     180.81644      30.27184 1.48734                                        52     728.32004      0.48766                                                 53     119.02258      38.20547 1.48734                                        54     609.84003      3.61782                                                 55     1650.31000     19.05217 1.61298                                        56     77.86795       17.17240                                                57     81.07073       30.61882 1.48734                                        58     -335.26499     2.16189                                                 59     -316.96290     26.15191 1.61536                                        60     -848.55009     (Bf)                                                    ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Correspondent Values to the Conditions for Third                              Embodiment                                                                    (1) f1 /L = 0.117                                                             (2) f2 /L = -0.0288                                                           (3) f3 /L = 0.106                                                             (4) f4 /L = -0.0762                                                           (5) f5 /L = 0.0868                                                            (6) f6 /L = 0.147                                                             (7) I/L = 2.87                                                                (8) f4A/f4B = 2.69                                                            (9) (r2Ff - r2Fr) / (r2Ff + r2Fr) = 1.15                                      (10) (r4N - r4P) / (r4N + r4P) = 0.0383                                       (11) |r4N/L| = 0.246                                        (12) |r4P/L| = 0.228                                        (13) f22/f23 = 1.13                                                           (14) (r5p - r5n) / (r5p + r5n) = 0.207                                        (15) (r5R - r6F) / (r5R + r6F) = -0.0202                                      (16) d56/L = 0.0156                                                           (17) d6 /r6F = 0.987                                                          (18) (r5F - r5R) / (r5F + r5R) = 0.910                                        (19) f21/L = 0.324                                                            (20) f2F/f2R = 0.521                                                          ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        Fourth Embodiment                                                             dO = 83.70761                                                                 β = 1/5                                                                  NA = 0.57                                                                     Bf = 21.09296                                                                 L = 1100                                                                             r              d        n                                              1      1185.70800     19.00074 1.61298                                        2      477.18400      6.60188                                                 3      1060.88800     30.01023 1.61536                                        4      -338.64042     1.12825                                                 5      200.00000      32.71424 1.61536                                        6      -2276.77900    1.25667                                                 7      248.82758      26.27974 1.61536                                        8      -1078.61200    3.19741                                                 9      -726.49629     15.60000 1.61298                                        10     110.53957      25.83515                                                11     2000.00000     19.48735 1.48734                                        12     -236.03800     3.28431                                                 13     -3000.00000    16.35209 1.61536                                        14     109.86653      32.21675                                                15     -153.78948     12.94478 1.61536                                        16     226.94451      35.22505                                                17     -132.31662     12.89677 1.61536                                        18     -830.43817     15.00000                                                19     -330.52996     22.58245 1.61536                                        20     -184.59786     0.39125                                                 21     -1874.03800    28.55306 1.61536                                        22     -221.73570     0.72991                                                 23     558.10318      33.51075 1.61536                                        24     -552.83568     0.96043                                                 25     478.84376      25.74084 1.48734                                        26     -906.26315     0.33363                                                 27     287.03514      23.69782 1.48734                                        28     2359.17900     0.83738                                                 29     201.46068      26.38775 1.48734                                        30     155.19710      46.91024                                                31     198.66962      27.76454 1.61536                                        32     122.40099      26.77778                                                33     -220.19752     13.01538 1.61298                                        34     3835.74700     12.87579                                                35     -180.57897     13.15020 1.61298                                        36     270.91501      0.55149                                                 37     250.92650      15.66663 1.48734                                        38     702.02997      25.47244                                                39     -1387.52600    15.36200 1.61298                                        40     404.60733      0.73901                                                 41     437.56855      27.62162 1.48734                                        42     -242.82524     0.51051                                                 43     476.89455      34.23933 1.48734                                        44     -364.55546     0.49298                                                 45     500.11721      34.15684 1.61536                                        46     -381.64661     9.55181                                                 47     -243.22857     18.84686 1.61298                                        48     -378.77918     0.50392                                                 49     355.95061      30.00332 1.61536                                        50     6474.81200     0.49017                                                 51     171.50098      30.27184 1.48734                                        52     722.00626      0.48766                                                 53     113.44841      38.20547 1.48734                                        54     442.83450      3.61782                                                 55     730.67537      19.05217 1.61298                                        56     73.59136       17.17240                                                57     78.92998       30.61882 1.48734                                        58     -315.11137     2.16189                                                 59     -286.11801     26.15191 1.61536                                        60     -878.71576     (Bf)                                                    ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        Correspondent Values to the Conditions for Fourth                             Embodiment                                                                    (1) f1 /L = 0.119                                                             (2) f2 /L = -0.0278                                                           (3) f3 /L = 0.106                                                             (4) f4 /L = -0.0675                                                           (5) f5 /L = 0.0805                                                            (6) f6 /L = 0.146                                                             (7) I/L = 2.29                                                                (8) f4A/f4B = 1.94                                                            (9) (r2Ff - r2Fr) / (r2Ff + r2Fr) = 1.36                                      (10) (r4N - r4P) / (r4N + r4P) = 0.0383                                       (11) |r4N/L| = 0.246                                        (12) |r4P/L| = 0.228                                        (13) f22/f23 = 1.17                                                           (14) (r5p - r5n) / (r5p + r5n) = 0.222                                        (15) (r5R - r6F) / (r5R + r6F) = -0.0350                                      (16) d56/L = 0.0156                                                           (17) d6 /r6F = 1.01                                                           (18) (r5F - r5R) / (r5F + r5R) = 0.817                                        (19) f21/L = 0.395                                                            (20) f2F/f2R = 0.603                                                          ______________________________________                                    

Letting L be the distance (object-to-image distance) from the objectplane P1 (reticle plane) to the image plane P2 (wafer plane) and Φ be arefractive power of lens surface in the sixth lens group G₆, in thefirst embodiment as described previously, 1/|ΦL|=0.130 for theobject-side lens surface of the positive lens L₆₁ and 1/|ΦL|=0.532 forthe object-side lens surface of the negative lens L₆₂, thus satisfyingthe condition (21). In the second embodiment, 1/|ΦL|=0.130 for theobject-side lens surface of the positive lens L₆₁ and 1/|ΦL|=0.550 forthe object-side lens surface of the negative lens L₆₂, thus satisfyingthe condition (21). In the third embodiment, 1/|ΦL|=0.151 for theobject-side lens surface of the positive lens L₆₁ and 1/|ΦL|=0.468 forthe object-side lens surface of the negative lens L₆₂, thus satisfyingthe condition (21). In the fourth embodiment, 1/|ΦL|=0.147 for theobject-side lens surface of the positive lens L₆₁ and 1/|ΦL|=0.423 forthe object-side lens surface of the negative lens L₆₂, thus satisfyingthe condition (21).

As described above, the sixth lens group G₆ in each embodiment iscomposed of three or less lenses including the lens surfaces satisfyingthe condition (21).

It is understood from the above values of specifications for therespective embodiments that the projection optical systems according tothe embodiments achieved satisfactory telecentricity on the object side(reticle R side) and on the image side (wafer W side) as securing thelarge numerical apertures and wide exposure areas.

FIG. 7 to FIG. 22 are respectively aberration diagrams to showaberrations in the first to fourth embodiments. Each of FIGS. 7, 11, 15,and 19 shows a spherical aberration of each embodiment. Each of FIGS. 8,12, 16, and 20 shows an astigmatism of each embodiment. Each of FIGS. 9,13, 17, and 21 shows a distortion of each embodiment. Each of FIGS. 10,14, 18, and 22 shows a coma of each embodiment.

Here, in each aberration diagram, NA represents the numerical apertureof the projection optical system 1, and Y the image height, and in eachastigmatism diagram, the dashed line represents the meridional imagesurface and the solid line the sagittal image surface.

It is understood from comparison of the aberration diagrams that theaberrations are corrected in a good balance in each embodiment even witha wide exposure area (image height) and a large numerical aperture,particularly, distortion is extremely well corrected up to nearly zerothroughout the entire image, thus achieving the projection opticalsystem with high resolving power in a wide exposure area.

The above-described embodiments showed the examples using the mercurylamp as a light source for supplying the exposure light of the i-line(365 nm), but it is needless to mention that the invention is notlimited to the examples; for example, the invention may employ lightsources including a mercury lamp supplying the exposure light of theg-line (435 nm), and extreme ultraviolet light sources such as excimerlasers supplying light of 193 nm or 248 nm.

In the above each embodiment the lenses constituting the projectionoptical system are not cemented to each other, which can avoid a problemof a change of cemented surfaces with time. Although in the above eachembodiment the lenses constituting the projection optical system aremade of a plurality of optic materials, they may be made of a singleglass material, for example quartz (SiO₂) if the wavelength region ofthe light source is not a wide band.

As described above, the projection optical system according to thepresent invention can achieve the bitelecentricity in a compact designas securing a wide exposure area and a large numerical aperture, and theinvention can achieve the projection optical system with high resolvingpower corrected in a good balance for aberrations, particularlyextremely well corrected for distortion.

From the invention thus described, it will be obvious that the inventionmay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims. The basicJapanese Application No. 872/1995 filed on Jan. 6, 1995 is herebyincorporated by reference.

What is claimed is:
 1. A projection optical system provided between afirst object and a second object, for projecting an image of a firstobject onto a second object, said projection optical system comprising afirst lens group with a positive refracting power, a second lens groupwith a negative refracting power, a third lens group with a positiverefracting power, a fourth lens group with a negative refracting power,a fifth lens group with a positive refracting power, and a sixth lensgroup with a positive refracting power in order from the side of saidfirst object,wherein said second lens group comprises a front lens witha negative refracting power disposed as closest to said first object andshaped with a concave surface to said second object, a rear lens of anegative meniscus shape disposed as closest to said second object andshaped with a concave surface to said first object, and an intermediatelens group disposed between said front lens and said rear lens, saidintermediate lens group having a first lens with a positive refractingpower, a second lens with a negative refracting power, and a third lenswith a negative refracting power in order from the side of said firstobject, and wherein when f₁ is a focal length of said first lens group,f₂ is a focal length of said second lens group, f₃ is a focal length ofsaid third lens group, f₄ is a focal length of said fourth lens group,f₅ is a focal length of said fifth lens group, f₆ is a focal length ofsaid sixth lens group, and L is a distance from said first object tosaid second object, the following conditions are satisfied:

    f.sub.1 /L<0.8

    -0.033 <f.sub.2 /L

    0.01 <f.sub.3 /L<1.0

    f.sub.4 /L<-0.005

    0.01 <f.sub.5 /L<0.9

    0.02 <f.sub.6 /L<1.6.


2. A projection optical system according to claim 1, wherein when I isan axial distance from said first object to a first-object-side focalpoint of said entire projection optical system and L is the distancefrom said first object to said second object, the following condition issatisfied:

    1.0 <I/L.


3. A projection optical system according to claim 1, wherein said fourthlens group comprises:a front lens group disposed as closest to the firstobject, said front lens group having two negative meniscus lenses eachshaped with a concave surface to said second object; a rear lens groupdisposed as closest to the second object, said rear lens group having anegative lens with a concave surface to said first object; and anintermediate lens group disposed between said front lens group in saidfourth lens group and said rear lens group in said fourth lens group,said intermediate lens group having first and second negative lenses inorder from the side of said first object, and wherein when f_(4A) is afocal length of said first negative lens in said fourth lens group andf_(4B) is a focal length of said second negative lens in said fourthlens group, the following condition is satisfied:

    0.05<f.sub.4A /f.sub.4B <20.


4. A projection optical system according to claim 1, wherein whenr_(2Ff) is a radius of curvature of a first-object-side surface of saidfront lens and r_(2Fr) is a radius of curvature of a second-object-sidesurface of said front lens, the front lens in said second lens groupsatisfies the following condition:

    1.00≦(r.sub.2Ff -r.sub.2Fr)/(r.sub.2Ff +r.sub.2Fr)<5.0.


5. A projection optical system according to claim 1, wherein said fourthlens group has:a front lens group having a negative lens disposed asclosest to said first object and shaped with a concave surface to saidsecond object; a rear lens group having a negative lens disposed asclosest to the second object and shaped with a concave surface to saidfirst object; and an intermediate lens group having a negative lens anda positive lens with a convex surface adjacent to a concave surface ofsaid negative lens is disposed between said front lens group in saidfourth lens group and said rear lens group in said fourth lens group,and wherein when r_(4N) is a radius of curvature of said concave surfaceof the negative lens in said intermediate lens group and r_(4P) is aradius of curvature of said convex surface of the positive lens in saidintermediate lens group, the following condition is satisfied:

    -0.9<(r.sub.4N -r.sub.4P) / (r.sub.4N +r.sub.4P)<0.9,

provided that when L is the distance from said first object to saidsecond object, said concave surface of said negative lens in saidintermediate lens group or said convex surface of said positive lens insaid intermediate lens group satisfies at least one of the followingconditions:

    |r.sub.4N /L|<2.0

    |r.sub.4P /L|<2.0.


6. A projection optical system according to claim 1, wherein when f₂₂ isa focal length of the second lens with the negative refracting power insaid second lens group and f₂₃ is a focal length of the third lens withthe negative refracting power in said second lens group, the followingcondition is satisfied:

    0.1<f.sub.22 /f.sub.23 <10.


7. A projection optical system according to claim 1, wherein said fifthlens group has a negative meniscus lens, and a positive lens disposed asadjacent to a concave surface of said negative meniscus lens and havinga convex surface opposed to the concave surface of said negativemeniscus lens, andwherein when r_(5n) is a radius of curvature of theconcave surface of said negative meniscus lens in said fifth lens groupand r_(5P) is a radius of curvature of the convex surface, opposed tothe concave surface of the negative meniscus lens, of the positive lensdisposed as adjacent to the concave surface of said negative meniscuslens in said fifth lens group, the following condition is satisfied:

    0<(r.sub.5P -r.sub.5n)/(r.sub.5P +r.sub.5n)<1.


8. A projection optical system according to claim 7, wherein saidnegative meniscus lens and said positive lens adjacent to the concavesurface of said negative meniscus lens are disposed between at least onepositive lens in said fifth lens group and at least one positive lens insaid fifth lens group.
 9. A projection optical system according to claim1, wherein said fifth lens group has a negative lens disposed as closestto the second object and shaped with a concave surface to the secondobject and the sixth lens group has a lens disposed as closest to thefirst object and shaped with a convex surface to the first object,andwherein when r_(5R) is a radius of curvature of a second-object-sidesurface of the negative lens disposed as closest to the second object insaid fifth lens group and r_(6F) is a radius of curvature of afirst-object-side surface of the lens disposed as closest to the firstobject in said sixth lens group, the following condition is satisfied:

    -0.90<(r.sub.5R -r.sub.6F)/(r.sub.5R +r.sub.5F)<-0.001.


10. A projection optical system according to claim 1, wherein when d₅₆is a lens group separation between said fifth lens group and said sixthlens group and L is the distance from said first object to said secondobject, the following condition is satisfied:

    d.sub.56 /L <0.017.


11. A projection optical system according to claim 1, wherein whenr_(6F) is a radius of curvature of a lens surface closest to the firstobject in said sixth lens group and d₆ is an axial distance from thelens surface closest to the first object in said sixth lens group to thesecond object, the following condition is satisfied:

    0.50<d.sub.6 /r.sub.6F <1.50.


12. A projection optical system according to claim 1, wherein said fifthlens group has a negative lens disposed as closest to the second objectand shaped with a concave surface to the second object, and wherein whenr_(5F) is a radius of curvature of a first-object-side surface of thenegative lens disposed as closest to the second object in said fifthlens group and r_(5R) is a radius of curvature of a second-object-sidesurface of the negative lens disposed as closest to the second object insaid fifth lens group, the following condition is satisfied:

    0.30<(r.sub.5F -r.sub.5R)/(r.sub.5F +r.sub.5R)<1.28.


13. A projection optical system according to claim 1, wherein when f₂ isa focal length of the first lens with the positive refracting power inthe intermediate lens group in said second lens group and L is thedistance from said first object to said second object, the followingcondition is satisfied:

    0.230<f.sub.21 /L<0.40.


14. A projection optical system according to claim 1, wherein whenf_(2F) is a focal length of the front lens with the negative refractingpower disposed as closest to the first object in said second lens groupand shaped with the concave surface to said second object and f_(2R) isa focal length of the rear lens with the negative refracting powerdisposed as closest to the second object in said second lens group andshaped with the concave surface to said first object, the followingcondition is satisfied:

    0<f.sub.2F /f.sub.2R <18.


15. A projection optical system according to claim 1, wherein theintermediate lens group in said second lens group has a negativerefracting power.
 16. A projection optical system according to claim 1,wherein said first lens group has at least two positive lenses, saidthird lens group has at least three positive lenses, said fourth lensgroup has at least three negative lenses, said fifth lens group has atleast five positive lenses and at least one negative lens, and saidsixth lens group has at least one positive lens.
 17. A projectionoptical system according to claim 1, wherein said sixth lens groupcomprises three or less lenses having at least one lens surfacesatisfying the following condition:

    1/|φL|<20

where φ: a refractive power of said lens surface, and L: theobject-to-image distance from said first object to said second object.18. A projection optical system according to claim 1, wherein amagnification of said projection optical system is 1/5.
 19. A method formanufacturing integrated circuits, said method including an exposureprocess of projecting an image of a pattern on a mask onto aphotosensitive substrate with an exposure light of a predeterminedwavelength, said exposure process comprising the steps of;supplying saidexposure light; introducing said exposure light to said mask; makingsaid exposure light passing through said mask incident on a projectionoptical system according to claim 1; and introducing said exposure lightpassing through said projection optical system onto said photosensitivesubstrate.
 20. A projection optical system according to claim 1, whereinsaid fifth lens group comprises a negative lens placed as closet to thesecond object and having a concave surface opposed to the second object.21. A projection optical system according to claim 20, wherein when d₅₆is a lens group separation between said fifth lens group and said sixthlens group and L is the distance from said first object to said secondobject, the following condition is satisfied:

    d.sub.56 /L<0.017.


22. A projection optical system according to claim 20, wherein whenr_(6F) is a radius of curvature of a lens surface closest to the firstobject in said sixth lens group and d₆ is an axial distance from thelens surface closest to the first object in said sixth lens group to thesecond object, the following condition is satisfied:0.50<d₆ /r_(6F)<1.50.
 23. A projection optical system according to claim 20, whereinsaid sixth lens group comprises three or less lenses having at least onelens surface satisfying the following condition:

    1/|φL|<20

where φ: a refractive power of said lens surface, and L: theobject-to-image distance from said first object to said second object.24. A projection optical system according to claim 16, wherein when I isan axial distance from said first object to a first-object-side focalpoint of said entire projection optical system and L is the distancefrom said first object to said second object, the following condition issatisfied:

    1.0<I/L.


25. A projection optical system according to claim 24, wherein saidfifth lens group has a negative meniscus lens, and a positive lensdisposed as adjacent to a concave surface of said negative meniscus lensand having a convex surface opposed to the concave surface of saidnegative meniscus lens, andwherein when r_(5n) is a radius of curvatureof the concave surface of said negative meniscus lens in said fifth lensgroup and r_(5P) is a radius of curvature of the convex surface, opposedto the concave surface of the negative meniscus lens, of the positivelens disposed as adjacent to the concave surface of said negativemeniscus lens in said fifth lens group, the following condition issatisfied:

    0<(r.sub.5p -r.sub.5n) /(r.sub.5p +r.sub.5n)<1.


26. A projection optical system according to claim 25, wherein saidnegative meniscus lens and said positive lens adjacent to the concavesurface of said negative meniscus lens are disposed between at least onepositive lens in said fifth lens group and at least one positive lens insaid fifth lens group.
 27. A projection optical system according toclaim 26, wherein said fifth lens group comprises a negative lens placedas closest to the second object and having a concave surface opposed tothe second object.
 28. A projection optical system according to claim27, wherein when r_(6F) is a radius of curvature of a lens surfaceclosest to the first object in said sixth lens group and d₆ is an axialdistance from the lens surface closest to the first object in said sixthlens group to the second object, the following condition is satisfied:

    0.50<d.sub.6 /r.sub.6F <1.50.


29. A projection optical system according to claim 28, wherein when f₂₂is a focal length of the second lens with the negative refracting powerin said second lens group and f₂₃ is a focal length of the third lenswith the negative refracting power in said second lens group, thefollowing condition is satisfied:

    0.1<f.sub.22 /f.sub.23 <10.


30. A projection optical system according to claim 29, wherein when f₂₁is a focal length of the first lens with the positive refracting powerin the intermediate lens group in said second lens group and L is thedistance from said first object to said second object, the followingcondition is satisfied:

    0.230<f.sub.21 /L<0.40.


31. A method for manufacturing integrated circuits, said methodincluding an exposure process of projecting an image of a pattern on amask onto a photosensitive substrate with an exposure light of apredetermined wavelength, said exposure process comprising the stepsof:supplying said exposure light; introducing said exposure light tosaid mask; making said exposure light passing through said mask incidenton a projection optical system according to claim 30; and introducingsaid exposure light passing through said projection optical system ontosaid photosensitive substrate.
 32. A method for manufacturing integratedcircuits, said method including an exposure process of projecting animage of a pattern on a mask onto a photosensitive substrate with anexposure light of a predetermined wavelength, said exposure processcomprising the steps of:supplying said exposure light; introducing saidexposure light to said mask; making said exposure light passing throughsaid mask incident on a projection optical system according to claim 28;and introducing said exposure light passing through said projectionoptical system onto said photosensitive substrate.
 33. A projectionoptical system according to claim 24, wherein said fourth lens groupcomprises:a front lens group disposed as closest to the first object,said front lens group having two negative meniscus lenses each shapedwith a concave surface to said second object; a rear lens group disposedas closest to the second object, said rear lens group having a negativelens with a concave surface to said first object; and an intermediatelens group disposed between said front lens group in said fourth lensgroup and said rear lens group in said fourth lens group, saidintermediate lens group having first and second negative lenses in orderfrom the side of said first object, and wherein when f_(4A) is a focallength of said first negative lens in said fourth lens group and f_(4B)is a focal length of said second negative lens in said fourth lensgroup, the following condition is satisfied:

    0.05<f.sub.4A /f.sub.4B <20.


34. A projection optical system according to claim 24, wherein whenr_(Ff) is a radius of curvature of a first-object-side surface of saidfront lens and r_(Fr) is a radius of curvature of a second-object-sidesurface of said front lens, the front lens in said second lens groupsatisfies the following condition:

    1.00<(r.sub.2Ff -r.sub.2Fr)/ (r.sub.2Ff +r.sub.2Fr)<5.0


35. A projection optical system according to claim 24, wherein saidfourth lens group has:a front lens group having a negative lens disposedas closest to said first object and shaped with a concave surface tosaid second object; a rear lens group having a negative lens disposed asclosest to the second object and shaped with a concave surface to saidfirst object; and an intermediate lens group having a negative lens anda positive lens with a convex surface adjacent to a concave surface ofsaid negative lens is disposed between said front lens group in saidfourth lens group and said rear lens group in said fourth lens group,and wherein when r_(4N) is a radius of curvature of said concave surfaceof the negative lens in said intermediate lens group and r_(4P) is aradius of curvature of said convex surface of the positive lens in saidintermediate lens group, the following condition is satisfied:

    -0.9<(r.sub.4N -r.sub.4P) /(r.sub.4N +r.sub.4P)<0.9,

provided that when L is the distance from said first object to saidsecond object, said concave surface of said negative lens in saidintermediate lens group or said convex surface of said positive lens insaid intermediate lens group satisfies at least one of the followingconditions:

    |r.sub.4N /L|<2.0

    |r.sub.4P /L|<2.0.


36. A projection optical system according to claim 24, wherein saidfifth lens group comprises a negative lens placed as closest to thesecond object and having a concave surface opposed to the second object.37. A projection optical system according to claim 36, wherein whenr_(6F) is a radius of curvature of a lens surface closest to the firstobject in said sixth lens group and d₆ is an axial distance from thelens surface closest to the first object in said sixth lens group to thesecond object, the following condition is satisfied:

    0.50<d.sub.6 /r.sub.6F <1.50.


38. A projection optical system according to claim 37, wherein when f₂₂s a focal length of the second lens with the negative refracting powerin said second lens group and f₂₃ is a focal length of the third lenswith the negative refracting power in said second lens group, thefollowing condition is satisfied:

    0.1<f.sub.22 /f.sub.23 <10.


39. A projection optical system according to claim 38, wherein when f₂₁is a focal length of the first lens with the positive refracting powerin the intermediate lens group in said second lens group and L is thedistance from said first object to said second object, the followingcondition is satisfied:

    0.230<f.sub.21 /L<0.40.


40. A method for manufacturing integrated circuits, said methodincluding an exposure process of projecting an image of a pattern on amask onto a photosensitive substrate with an exposure light of apredetermined wavelength, said exposure process comprising the stepsof:supplying said exposure light; introducing said exposure light tosaid mask; making said exposure light passing through said mask incidenton a projection optical system according to claim 39; and introducingsaid exposure light passing through said projection optical system ontosaid photosensitive substrate.
 41. A projection optical system accordingto claim 24, wherein when f₂₂, is a focal length of the second lens withthe negative refracting power in said second lens group and f₂₃ is afocal length of the third lens with the negative refracting power insaid second lens group, the following condition is satisfied:

    0.1<f.sub.22 /f.sub.23 <10.


42. A projection optical system according to claim 41, wherein when f₂₁is a focal length of the first lens with the positive refracting powerin the intermediate lens group in said second lens group and L is thedistance from said first object to said second object, the followingcondition is satisfied:

    0.230<f.sub.21 /L<0.40.


43. A projection optical system according to claim 24, wherein when f₂₁is a focal length of the first lens with the positive refracting powerin the intermediate lens group in said second lens group and L is thedistance from said first object to said second object, the followingcondition is satisfied:

    0.230<f.sub.21 /L<0.40.


44. A method for manufacturing integrated circuits, said methodincluding an exposure process of projecting an image of a pattern on amask onto a photosensitive substrate with an exposure light of apredetermined wavelength, said exposure process comprising the stepsof:supplying said exposure light; introducing said exposure light tosaid mask; making said exposure light passing through said mask incidenton a projection optical system according to claim 24; and introducingsaid exposure light passing through said projection optical system ontosaid photosensitive substrate.
 45. A projection optical system accordingto claim 16, wherein said fifth lens group has a negative meniscus lens,and a positive lens disposed as adjacent to a concave surface of saidnegative meniscus lens and having a convex surface opposed to theconcave surface of said negative meniscus lens, andwherein when r_(5n)is a radius of curvature of the concave surface of said negativemeniscus lens in said fifth lens group and r_(5P) is a radius ofcurvature of the convex surface, opposed to the concave surface of thenegative meniscus lens, of the positive lens disposed as adjacent to theconcave surface of said negative meniscus lens in said fifth lens group,the following condition is satisfied:

    0<(r.sub.5p -r.sub.5n) /(r.sub.5p +r.sub.5n)<1.


46. A projection optical system according to claim 45, wherein saidnegative meniscus lens and said positive lens adjacent to the concavesurface of said negative meniscus lens are disposed between at least onepositive lens in said fifth lens group and at least one positive lens insaid fifth lens group.
 47. A method for manufacturing integratedcircuits, said method including an exposure process of projecting animage of a pattern on a mask onto a photosensitive substrate with anexposure light of a predetermined wavelength, said exposure processcomprising the steps of:supplying said exposure light; introducing saidexposure light to said mask; making said exposure light passing throughsaid mask incident on a projection optical system according to claim 46;and introducing said exposure light passing through said projectionoptical system onto said photosensitive substrate.
 48. An exposureapparatus comprising:a stage allowing a photosensitive substrate to beheld on a main surface thereof; an illumination optical system foremitting exposure light of a predetermined wavelength and transferring apredetermined pattern of a mask onto said substrate; and a projectionoptical system provided between said mask and said substrate, saidprojection optical system including a first lens group with a positiverefracting power, a second lens group with a negative refracting power,a third lens group with a positive refracting power, a fourth lens groupwith a negative refracting power, a fifth lens group with a positiverefracting power, and a sixth lens group with a positive refractingpower in order from the side of said mask, wherein said second lensgroup comprises a front lens with a negative refracting power disposedas closest to said first object and shaped with a concave surface tosaid second object, a rear lens of a negative meniscus shape disposed asclosest to said second object and shaped with a concave surface to saidmask, and an intermediate lens group disposed between said front lensand said rear lens, said intermediate lens group having a first lenswith a positive refracting power, a second lens with a negativerefracting power, and a third lens with a negative refracting power inorder from the side of said mask, and wherein when f₁ is a focal lengthof said first lens group, f₂ is a focal length of said second lensgroup, f₃ is a focal length of said third lens group, f₄ is a focallength of said fourth lens group, f₅ is a focal length of said fifthlens group, f₆ is a focal length of said sixth lens group, and L is adistance from said mask to said substrate, the following conditions aresatisfied: f₁ /L<0.8 -0.033<f₂ /L 0.01<f₃ /L<1.0 f₄ /L<-0.005 0.01<f₅/L<0.9 0.02<f₆ /L<1.6.
 49. An exposure apparatus according to claim 48,wherein a magnification of said projection optical system is 1/5.
 50. Anexposure apparatus according to claim 48, wherein said first lens grouphas at least two positive lenses, said third lens group has at leastthree positive lenses, said fourth lens group has at least threenegative lenses, said fifth lens group has at least five positive lensesand at least one negative lens, and said sixth lens group has at leastone positive lens.
 51. An exposure apparatus according to claim 50,wherein when I is an axial distance from said first object to afirst-object-side focal point of said entire projection optical systemand L is the distance from said first object to said second object, thefollowing condition is satisfied:

    1.0<I/L.


52. An exposure apparatus according to claim 51, wherein said fifth lensgroup has a negative meniscus lens, and a positive lens disposed asadjacent to a concave surface of said negative meniscus lens and havinga convex surface opposed to the concave surface of said negativemeniscus lens, andwherein when r_(5n) is a radius of curvature of theconcave surface of said negative meniscus lens in said fifth lens groupand r_(5P) is a radius of curvature of the convex surface, opposed tothe concave surface of the negative meniscus lens, of the positive lensdisposed as adjacent to the concave surface of said negative meniscuslens in said fifth lens group, the following condition is satisfied:

    0<(r.sub.5p -r.sub.5n) /(r.sub.5P +r.sub.5n)<1.


53. An exposure apparatus according to claim 52, wherein said negativemeniscus lens and said positive lens adjacent to the concave surface ofsaid negative meniscus lens are disposed between at least one positivelens in said fifth lens group and at least one positive lens in saidfifth lens group.
 54. An exposure apparatus according to claim 51,wherein said fifth lens group comprises a negative lens placed asclosest to the second object and having a concave surface opposed to thesecond object.
 55. An exposure apparatus according to claim 54, whereinwhen r_(6F) is a radius of curvature of a lens surface closest to thefirst object in said sixth lens group and d₆ is an axial distance fromthe lens surface closest to the first object in said sixth lens group tothe second object, the following condition is satisfied:

    0.50<d.sub.6 /r.sub.6F <1.50.


56. An exposure apparatus according to claim 51, wherein when f₂₂ is afocal length of the second lens with the negative refracting power insaid second lens group and f₂₃ is a focal length of the third lens withthe negative refracting power in said second lens group, the followingcondition is satisfied:

    0.1<f.sub.22 /f.sub.23 <10.


57. An exposure apparatus according to claim 51, wherein when f₂₁ is afocal length of the first lens with the positive refracting power in theintermediate lens group in said second lens group and L is the distancefrom said first object to said second object, the following condition issatisfied:

    0.230<f.sub.21 /L<0.40.